Microcapsules of poly(methyl metharcylate) containing epoxy resin and multi-walled carbon nanotubes

Abstract

Microcapsules of poly(methyl methacrylate) [PMMA] containing epoxy and multi-walled carbon nanotubes were formed by solution evaporation in an aqueous emulsion. Thin PMMA shells precipitated at the resin/water interface as the solvent was removed, thus encapsulating the dispersion of epoxy and nanotubes. Dichloromethane (DCM) was selected as the common solvent for both resin and PMMA, and slowly evaporated from the aqueous mixture agitated at 40°C. After trying various epoxy/PMMA ratios, a 1:1 w/w epoxy/PMMA ratio yielded stable, individual microcapsules with smooth PMMA shells. Four different mixing speeds (300, 500, 800, and 1000 rpm) and four carbon nanotube contents (0.25, 0.50, 1.00, 2.00 w/w %) were used during the encapsulation process. Microcapsules with 10 to 55 μm average diameter were obtained by increasing the mixing speed from 300 to 1000 rpm. Increasing the mixing speed yielded a decrease in average particle size, whereas carbon nanotube presence led to a broader capsule size distribution at any given mixing speed. In addition, roughness of the microcapsule surface increased with increasing carbon nanotube content and mixing speed. SEM images of microcapsules showed that microcapsules with various types of core-shell morphology were formed during the encapsulation process.